Figure 1.
Abbreviations: BMI: body mass index; mMRC: modified Medical Research Council; CCQ: clinical COPD questionnaire; TGV: thoracic gas volume and DLCO: diffusing capacity of the lung for carbon monoxide.
Table 1.
Description of the 527 COPD patients based on spirometric GOLD classification.
Figure 2.
Dendrogram illustrating the results of the cluster analysis in 527 COPD subjects.
Subjects were classified using agglomerative hierarchical cluster analysis based on the main axes identified by principal component analysis (PCA) and multiple correspondence analyses (MCA, see Methods section). Each vertical line represents an individual subject and the length of vertical lines represents the degree of similarity between subjects. The horizontal lines identify possible cut-off for choosing the optimal number of clusters in the data. When choosing 3 clusters (upper line) the 3 groups (labelled 1 to 3) have differential mortality rates (0.5%, 20.6% and 14.3% for Phenotype 1, 2, and 3, respectively). When choosing 5 clusters (lower line, labelled 1′ to 5′), subjects in clusters 1′ and 2′ had comparable mortality rates (0.7% and 0%, respectively) and subjects in clusters 4′ and 5′ had similar mortality rates (14.3% in each group), suggesting that grouping in 5 phenotypes would not improve patient classification.
Table 2.
Description of the 527 COPD patients based on phenotypes identified by cluster analysis.
Figure 3.
Mortality distribution by GOLD stage in Phenotype 2 and 3.
At the end of the follow-up period, 20/97 (20.6%) and 29/203 (14.3%) subjects had died in Phenotype 2 and 3, respectively. Distribution of dead subjects by GOLD stage is expressed as % total number of death in each phenotype. The majority of Phenotype 2 subjects who died had very severe airflow limitation, whereas only 25% of Phenotype 3 subjects who died were in GOLD stage IV.
Table 3.
Cox model analysis of mortality between phenotypes.
Figure 4.
Kaplan-Meier analysis of mortality between Phenotypes.
Subjects in Phenotype 2 and 3 were at higher risk of mortality than subjects in Phenotype 1 (each comparison, P<0.0001; log-rank test). However, no significant difference was observed between Phenotype 2 and 3, indicating that during the period of observation both group had comparable mortality.